Sheets, gloves, bags and the like coated with a vinyl chloride-based resin have great mechanical strength, and they exhibit excellent wear resistance, chemical resistance and oil resistance so that they can be used in various fields such as fishery, agriculture, mining and the like.
Conventionally, coating of the vinyl chloride-based resin on sheets, gloves, bags and the like has been performed by spraying or dipping of a plastisol containing vinyl chloride-based resin aggregate particles or a gelled melt prepared by heating the plastisol on a fabric.
Since a plastisol is a viscous liquid, when it is applied to a fabric or used for dipping, the plastisol may infiltrate into the fabric, sometimes into the back face of the fabric. Similarly, in a case of heating the plastisol, the gelled melt may infiltrate into the back face of the fabric. If the plastisol or the gelled melt infiltrates into the back face of the fabric, the flexibility of the coated product will deteriorate considerably, which harms the product functions. In particular, when it is applied to gloves, even if the infiltration is local, the obtained gloves will cause discomfort in wearing to the user, and degrade the commercial value.
For coping with such problems, there have been proposed vinyl chloride-based resins capable of lowering a property of plastisol of infiltrating into the fabric back face at the time of being coated on the fabric, i.e., capable of providing a plastisol with improved non-infiltrating property, and a method for producing the same. For example, Patent Document 1 proposes a method for heat-treating a vinyl chloride resin for paste in hot air at 60 to 140° C. for 5 minutes to 1 hour. Patent Document 2 proposes a vinyl chloride resin having a mean particle diameter of 20 to 50 μm that has been dried by a spray drier, with the outlet temperature set at 65° C. or higher. Patent Document 3 proposes a vinyl chloride resin having a specific particle size distribution, a certain level of resistance to disintegration strength, and a specific void volume. Patent Document 4 proposes a method for adding an infiltration suppressant, such as a copolymer of methyl vinyl ether and maleic anhydride, to a vinyl chloride resin latex and drying the mixture. Patent Document 5 proposes a method for drying a vinyl chloride resin latex that has been coagulated using a specific coagulant composed of a water-soluble polymer and an inorganic salt. Patent Document 6 proposes a method for using a vinyl chloride resin latex that has been polymerized using a specific acrylic monomer.
However, regarding plastisols containing the vinyl chloride-based resins proposed in the above-mentioned Patent Documents 1 to 6, although the non-infiltrating property is improved, the sagging property tends to be inferior to plastisols containing general-purpose vinyl chloride resin paste. If the sagging property of the plastisol is insufficient, when the plastisol is applied on a fabric glove or the like that has been mounted on a mold of a hand shape and excessive plastisol is to sag off from the product, the plastisol will adhere excessively to the fabric glove or the like. Such a glove on which plastisol adheres too much will be heavy and less flexible, and thus less comfortable in use.
Further, for the plastisol containing the vinyl chloride-based resin, an increase in viscosity over time (thickening over time) has been a technical problem for many years. For example, as disclosed in Non-Patent Documents 1 and 2, a phenomenon has been known that when di-2-ethylhexyl phthalate (general plasticizer) is used, the viscosity of sol increases significantly even with a slight change in the moisture content, such as due to absorption of moisture in air by the plasticizer. Such thickening over time of the sol decreases the sagging property of the plastisol.